EP 0 856 429 A1 discloses a seat rail pair in which four balls are provided between a lower rail and an upper rail. In each case two balls rest on the two sides of an obliquely inclined end section of the lower rail, which end section is adapted as a ball raceway in its shape to the balls. The upper rail encloses the balls on the respective other side with sections with a different inclination as ball raceways. The locking of the two seat rails is carried out by means of a bar which introduced off center. When there are unequal loads there is the risk of the balls leaving their raceways and causing adjacent regions of the rail profiles to become deformed i.e. the material becomes locally plastically deformed owing the high pressures and leaves behind marks in the form of spherical depressions or caterpillar-like depressions which, when the seat rails are adjusted, become perceptible in the form of undesired fluctuations in force and accelerations.